1. Field of the Invention
The present invention relates to the form of the transparent thickness section provided on the side of the color filter board of a liquid crystal display device.
2. Background Art
In one example of the semi-transmissive type of liquid crystal display devices of prior art, a picture element has a reflective part that utilizes environmental light to implement displays in the reflective mode and a transmissive part that utilizes a backlight to implement displays in the transmissive mode. FIG. 2 represents an extracted portion of a semi-transmissive type liquid crystal display device (cell) corresponding to a single picture element (picture electrode), and schematically presents a cross-sectional view of such portion.
As shown in FIG. 2, the bottom part of a picture electrode board 1 includes a transparent substrate 2 (typically a glass substrate), over which a picture electrode 4 is made to reside, and an interlayer film 3 is inserted there between, where necessary. On the left half side of the picture electrode 4, a reflecting plate 5 is provided at the boundary between the interlayer film 3 and the picture electrode 4, such left half portion constituting a reflective part 6. The right-half portion of the picture electrode 4, where the reflecting plate 5 is absent, represents the transmissive part 7.
As shown in FIG. 2, a color filter board 8 is deployed on the upper side opposite the picture electrode board 1. The distance between the two boards 1, 8 is determined by, for example, a rib 9, and the space between the two boards is filled with liquid crystal 10. On the surface of the color filter board 8 positioned opposite the picture electrode board 1, color filters CF are provided for three colors, namely, red (R), green (G) and blue (B).
However, whereas the light from the backlight (not shown in the drawing) passes only once through the liquid crystal layer in the transmissive part 7 of the conventional semi-transmissive type liquid crystal display device, the environmental light that enters through the glass filter board 8 in the reflective part 6 passes through the liquid crystal layer twice because it is reflected by the reflecting plate 5 of the picture electrode board 1. This means that the actual thickness of the liquid crystal layer as regards the transmitted light varies, and as a result it is necessary to implement gap control. To that end, a transparent thickness section 11 (a transparent layer) is provided over the color filter board 8, as disclosed in published literature pertaining to JP-A-2003-57433, where the transparent thickness section is referred to as a “transparent layer”. Together with the color filters CF, the transparent thickness section 11 composes a pixel element and is therefore usually formed so as to straddle the gaps between adjacent color filters.
In an ordinary liquid crystal display device (not shown), a transparent thickness section is formed on the surface of the color filter layer for the purpose of enhancing the flatness of the color filter layer, as well as protecting such color filter layer in cases where an opposing electrode (such as indium oxide film) is formed over such color filter layer, as disclosed in published literature pertaining to JP-A-7-261183.
In the process of manufacturing liquid crystal display devices, including semi-transmissive ones, after the transparent thickness section 11 is formed, an opposing electrode (indium oxide film) and an orientation film, (both not shown in the drawings), are formed over its surface. The orientation film is formed by applying polyimide resin or similar orientation agent with a roller or similar implement, then drying it. Such process however causes puddling of the surplus orientation agent, making the orientation film uneven and run in the direction roughly parallel to the direction in which the locally-formed transparent thickness sections 11 are lined up (in the direction of the width of the transparent thickness section 11, i.e., the direction perpendicular to the cross-sectional plane of FIG. 2).
Such unevenness in thickness of the orientation film gives rise to twists and irregularities in the orientation of the liquid crystal molecules, inducing orientation defects in them, as would lead to defective display as well as deterioration of display quality.